Myoclonus – Periodic Limb Movements

Last updated: May 10, 2019

The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.

Periodic limb movement disorder (PLMD or PLMS), formerly known as myoclonus, is a condition where a person suffers repetitive limb movements while sleeping. There is a sudden and uncontrollable twitching of a muscle or a group of muscles that occurs about every 20-50 seconds. These movements also operate at a cadence. Thus, “periodic”.

This condition is also classified as a sleep disorder. This happens during the course of a person’s sleep, causing interruption. This can be followed by severe daytime sleepiness and extreme exhaustion.

Take note that PLMD and Restless Leg Syndrome (RLS) are two different disorders and should not be confused with each other. RLS can happen both when a person is awake and asleep. The legs also promote a voluntary response to a feeling of distress in this case. On the other hand PLMD is involuntary. Its symptoms attack during sleep, causing a patient to be unaware of these movements.

What is the cause of PLMD?

Periodic Limb Movement Disorder can be classified into two categories. One is primary PLMD and the other one is secondary PLMD.

Primary PLMD

The definite cause of primary PLMD is anonymous even up to this day. Researchers suggest that this could be a cause of nerve abnormalities that are having difficulties conveying messages across the brain to the limbs. However, not one clinical study has led to a consistent result.

On the brighter side this is not considered a severe medical condition. As a matter of fact primary PLMD is uncommon, as affirmed by the National Sleep Foundation. Although if left untreated it may cause complications that could lead to more serious issues.

Secondary PLMD

Secondary PLMD on the other hand, could be caused by an abuse of a certain medication (e.g. Antihistamines, Antipsychotics, Antidepressants).

Most of the time this could be due to the following underlying medical issues:

  • Iron deficiency
  • Diabetes mellitus
  • Spinal cord injury
  • Spinal cord tumor

PLMD can also be triggered by the following:

  • Sleep apnea syndrome – breathing difficulties that occur during sleep, causing disturbance and lack of energy during the following day
  • Multiple system atrophy – a rare neurodegenerative disorder due to a dysfunction of the basal ganglia and ataxia
  • REM sleep behavior disorder (RBD) – a condition where a patient “acts out” his dreams that are often vivid and violent, causing sleep disruption
  • Narcolepsy – a sleep condition where a patient experiences excessive sleepiness and a persistent feeling of wanting to sleep during the daytime
  • Anemia – a condition wherein you don’t have enough hemoglobin to transport oxygen throughout the body’s tissues
  • Uremia – a serious complication of chronic kidney disease associated with an acute kidney injury caused by a build-up of waste products in the blood
  • Sudden withdrawal from sedatives such as benzodiazepines (Valium) or barbiturates

What are the symptoms of PLMD?

The primary symptom of PLMD is the uncontrollable and cadenced movement of limbs during sleep. However, as this happens during a person’s sleeping time, patients are completely unaware of these movements. Although people with PLMD may not notice this, it is their bedmates who get the signs, and their sleep is greatly affected and disturbed.

The more common symptoms of PLMD are sleep interruption/poor sleep, daytime sleepiness, and primary to chronic insomnia.

  • Sleep interruption/poor sleep Because these movements can be persistent and uncontrollable it can be disruptive. It can cause sleep interruption and numerous arousals. These sudden arousals happen in a short period of time. This can be hard to spot by the patient but with the help of a sleep test by brain wave analysis it can be captured.
  • Excessive daytime sleepiness – Sleep disruptions associated with this condition may cause extreme tiredness the following day. A person may feel a lack of drive and enthusiasm in his workplace when suffering from this condition.
  • Primary to chronic insomnia – Once a person becomes aware that he is suffering from periodic limb movement disorder (PLMD), he may start to become worried about not getting enough sleep. This leads to acquiring sleep disorders – particularly insomnia -where a person experiences difficulty in falling and staying asleep.

Who can acquire PLMD?

About 80% of people suffering from Restless Legs Syndrome are also diagnosed with PLMD. About 30% of these people are aged 65 and older.

Since researchers still can’t provide a consistent explanation about why PLMD occurs, the exact ratio of age is still unknown as well. As of now, based on present research, any person of any age can acquire this disorder. Although the likelihood of experiencing this disorder does not increase as you age.

This can also be acquired by any gender, unlike RLS.

Treatment of PLMD

It is important to remember that the treatment process of PLMD does not actually cure the entire disorder, especially if it’s primary PLMD, which still has no definite cause even up to this day. However, it helps the patient greatly cope with the burden and improve the symptoms.

These treatments are not recommended if movements associated with your PLMD do not affect your sleep habits. If they do, it can be countered in the following ways.

Caffeine avoidance

Caffeine is known to worsen symptoms of this movement disorder. Caffeine-containing foods often cause disrupted sleep. This is why it’s important to avoid food and drinks containing caffeine especially when you are diagnosed with sleep or movement disorders. Some of the common everyday food and drinks that contain caffeine include:

  • Coffee
  • Soda
  • Chocolate
  • Tea
  • Cereals

If you are diagnosed with secondary PLMD it can be treated by addressing the underlying medical symptoms with the help and advise of your medical doctor.

Additional references:

The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.